Just Cause is an open-world action-adventure third-person shooter developed by Avalanche Studios and published by Eidos Interactive. It was released on September 2006 for the PC, Playstation and Xbox platforms, and is the first game in the series, followed by Just Cause 2 released in 2010 and Just Cause 3 released in December 2015.

The story takes place in a fictional South American island called San Esperito, where Agency black ops agent Rico Rodriguez is tasked with aiding the local guerrilla factions in taking down the dictatorial rule of Salvador Mendoza; causing massive chaos and taking down dictators and their armies with heavy firepower would become Rico's modus operandi and best-known feature of the games.

The following weapons are seen in the video game Just Cause (2006 VG):

Pistols

All pistols are one-handed weapons in the game and can be dual-wielded. The Holdt P4 Pitbulls are always dual-wielded and take a separate slot of their own; the rest share one slot.

"Holdt P4 Pitbull"

Rico always carries a pair of Pitbulls as his fallback weapons. The Pitbulls are primarily based on the Taurus Raging Bull, and are fitted with unusable miniature grenade launchers based on the M203.
Despite their imposing profiles, they are the weakest weapons in the game.

The same gun would later appear as "Rico's Signatue Gun" in Just Cause 2.

Taurus Raging Bull with 6" barrel and stainless finish - .454 Casull

Rico holds a Pitbull.

FN Five-SeveN

The FN Five-seveN, called the "Moretti P.94," is a common weapon in the game and has a 15-round magazine. A suppressed version called the "Gallini M39 "Husher"" is also available: this holds only 8 rounds, but has the highest stopping power of the pistols (even more powerful than the revolvers). Its name is a reference to the Smith & Wesson Model 39, specifically the Mk22 "Hush Puppy" variant used by Navy SEALs.

FN Five-seveN USG (U.S. Government) model - FN 5.7x28mm

Rico holds a "P.94."

The "Husher" variant on the ground.

"Harker 357 Sawback"

The other revolver in-game, the Sawback is often wielded by San Esperito police officers. It is based on the Dan Wesson PPC.

Dan Wesson PPC Stainless Steel - .357 Magnum

The Sawback on the ground.

Submachine Guns

Except for the Aviv Panthera, all SMGs are dual-wielded.

Heckler & Koch UMP

The "Aviv Panthera" is a Heckler & Koch UMP with some additional G36 stylings, and is the only two-handed submachine gun in the game. It is commonly wielded by enemy soldiers.

Heckler & Koch UMP45 - .45 ACP

Rico holding the Panthera.

Brügger & Thomet MP9

The "Nova-9" is a one-handed SMG and the only suppressed SMG. It appears to be a misproportioned Brügger & Thomet MP9 with a misplaced ejection port, the back of the stock missing, and no front grip like a Steyr SPP.

Brügger & Thomet MP9 - 9x19mm

Rico holding the Nova. Note that most of the MP9's folded stock is present on the side of the receiver.

"Aviv Scarab"

Shotguns

"Dawson 61 Sports Model"

The Dawson 61 is a one-handed sawn-off shotgun commonly used guerrillas. A similar model that infamously holds 3 rounds appears as the "Sawn-off Shotgun" in Just Cause 2.

Stevens 311R (sawed-off) - 12 gauge

The Sports Model on the ground.

"Moretti CCW Centurion"

The Centurion is a magazine-fed automatic shotgun loosely based on the Hawk Semi-Auto Tactical shotgun. The foregrip and pump are reminiscent of the SPAS-12. The Centurion has a 6-round magazine.

Hawk Semi-Auto Tactical - 12 Gauge

Franchi SPAS-12 with butt hook attached to stock - 12 gauge

The Centurion on the ground.

"Moretti CCW Praetorian"

The Praetorian is another magazine-fed automatic shotgun, this time based on the SPAS-15 shotgun. It has double the magazine size of the Centurion at 12 rounds, but deals roughly half the damage. Like the Centurion, it also has the SPAS-12 pump and foregrip.

SPAS-15 - 12 Gauge

Franchi SPAS-12 with butt hook attached to stock - 12 gauge

The Centurion on the ground.

Assault Rifles

Heckler & Koch G36C

The Heckler & Koch G36C is the main assault rifle of the San Esperito military, called the "Adler FF M-72."

Heckler & Koch G36C - 5.56x45mm

The Adler on the ground.

Heckler & Koch XM8 Sharpshooter

The "Haswell Gen2 Vindicator" is a more accurate assault rifle than the G36, and is based on the sharpshooter version of the Heckler & Koch XM8.

Heckler & Koch XM8 Sharpshooter Rifle - 5.56x45mm

Rico holds the Vindicator.

The Vindicator on the ground.

"Fleisher AR-5 Blizzard"

One of the most powerful weapons in-game, the Blizzard feeds from a 60-round casket magazine. It appearance greatly resembles the M41A Pulse Rifle from Aliens with the stock of an M249 and the upper handguard of the XM29 OICW KE module.

M41A Pulse Rifle

The Adler on the ground.

Sniper Rifles

"Lance FDL"

The Lance FDL is a semi-automatic marksman rifle based on the Beretta RX4 with the stock of the CX4. It is fitted with a lengthened precision barrel and a scope.

"Barclay Phantom"

Launchers

"Mako Hammerhead"

A rotary grenade launcher loosely based on the Milkor MGL, with the carry handle and barrel vaguely reminiscent of the Pancor Jackhammer.

Milkor MGL fitted with Armson OEG reflex sight - 40x46mm

Rico holds the Hammerhead.

The Hammerhead on the ground.

"Mako Ocra"

The Ocra was likely misspelled and meant to be the Orca, but otherwise is a guided missile launcher that can somehow hold 3 missiles. It appears to be based primarily on the multi-shot rocket launcher from Far Cry, with the front of an Armbrust ATW on the back as an exhaust tube and the muzzle of a Mk 19 Grenade Launcher on the front.

Rico holds the Ocra.

The Ocra on the ground.

M72 LAW

The "RPG M-112" is a single-shot rocket launcher based heavily on the M72 LAW. It's held backwards.